The Jerrold Model 704 (including its variants the 704A and the 704B) holds a special place in the history of the cable television industry. During the 1960s, when most cable TV systems were carrying twelve channels (2-13), the 704 was the most popular signal level meter in use. An entire generation of system techs came of age using the 704.
The 704 incorporated a continuous tuner capable of tuning 54 to 220 MHz band. VHF Channels 2-13, and the FM broadcast band, were indicated. Although the meter was capable of tuning midband channels (98, 99, 14-22), they were not indicated on the tuning dial; only the corresponding off-air bands (aviation, amateur, telephone) were indicated.
The meter was not capable of tuning UHF, superband, or subband channels. To address the need to tune to these bands, Jerrold offered an adapter known as the TK-Channel Adapter This device was connected between the incoming test signal and the 704 input connector.
This device block-converted a desired band of frequencies to a band within the 704's tuning range. Richard Kreeger (who contributed one of the photos on this page) believes this adapter was designed to up convert the 5-47 MHz spectrum to 105-147 MHz. Kreeger also notes that "it was a unity gain device so it would read these signals directly from a level standpoint."
Graham Stubbs states:
For the "K" channels, used by Jerrold as part of a scheme to effect adjacent channel operation in the early 1950's, a special adaptor was provided which mounted on the outside of the cabinet.
Jerrold also offered a 300-ohm to 75-ohm transformer. This device matched a 300-ohm source (e.g., a dipole antenna) to the 75-ohm input of the 704B so that the 704 could be used to measure the field strength of an electromagnetic field.
The 704 has long since passed from the scene, but its memory lives on to this day, kept alive by an organization of mildly insane senior citizens known as the Loyal Order of the 704. Each year, during the annual SCTE Cable Tec Expo, the Loyal Order meets for an evening of ritual conviviality accompanied by the 704's mascot, a pink plastic flamingo named Pinky.
